Screening and Fermentation Condition Optimization for Antagonistic Bacteria to Phytophthora Nicotianae

In order to screen the bacterial strains which have antagonistic effects on Phytophthora nicotianae and provide favorable resources for the biological control of tobacco black shank disease in Henan tobacco areas, the rhizosphere soil samples of healthy tobacco plants were collected from tobacco black shank disease nursery and eight bacterial strains were screened by confrontation culture method. Among them, the strain LB-9 had the strongest and stable inhibitory effect on P. nicotianae with a bacteriostatic rate of 60.6% and a broad spectrum. The strain was identified as Paenibacillus polymyxa by 16S rRNA gene sequencing analysis. The optimum fermentation medium, temperature, time and initial pH value of LB-9 were determined by single factor optimization test which has great significance to the development and application of biocontrol agents.